The technology to which the invention is directed relates to a sealer used for asphalt substrates, such as a sealer for asphalt parking lots and driveways of the type employed extensively throughout the United States. Asphalt is comprised essentially of two components, aggregate and a binder. Aggregate for asphalt is a measured mixture of stone and sand, while the binder is a petroleum derivative. These components are combined, heated and blended in a batch plant. As soon as the asphalt is laid in a parking lot or driveway, the binder begins to evaporate and over time it decays by being exposed to the damaging effects of sun that causes oxidation, rain, snow and other environmental conditions. Gasoline, oil leaks and chemicals, such as ice control salt, also have a dramatic effect on the life of the binder in the asphalt. As the binder is destroyed by these external, unavoidable conditions, its ability to hold the aggregate together diminishes. This problem creates cracks, distortion and disintegration of the asphalt surface. After three to five years under normal conditions, major deterioration takes place and the parking lot or driveway must be resurfaced. To protect the asphalt from normal environmental deterioration, a thixotropic sealer is normally applied on top of the asphalt. This is done when the asphalt is first laid and upon subsequent repairs. In either situation, a thin layer of thick sealer is applied to the asphalt surface to protect the same from deterioration. The sealer preserves the elasticity of the asphalt binder by sealing out oxidizing effects of sun, salt and water, as well as petroleum spillage. The sealer or seal coat dries to an attractive uniform flat black layer creating a like new appearance for the asphalt surface. It is common practice to mix sand with the sealer to create a non-skid surface and increase the wear characteristics of the pavement. Generally asphalt sealers constitute a highly economical method of maintaining and extending the life of asphalt surfaces. The most common asphalt sealer is a water based solution of refined coal tar formed as an emulsion with a clay filler and added sand for increasing the wear resistance of the sealer. Clay has a very fine particle or grain size and is an excellent filler in the aqueous emulsion. Other additives are available to enhance specific characteristics of the sealer, such as adhesion characteristics, drying time, sand suspension and color of the sealer.
The present invention relates to a sealer for an asphalt surface, which novel sealer includes coal tar or asphalt pitch emulsified with clay and water. Of course, other additives are included in the novel sealer in accordance with standard technology. Preferably, the new sealer is a coal tar emulsion of coal tar pitch, clay and water, perhaps with an emulsifier or surfactant and other optional ingredients. Such sealers or seal coat are long lasting, have a pleasing black color and are resistant to gasoline and kerosene spills. As an alternative to the preferred coal tar emulsion sealer using the present invention, the sealer can comprise an asphalt based material formed from distilled petroleum fractions. Such heavy hydrocarbon fractions are sometimes used for asphalt based sealers; however, the most common sealer is a coal tar emulsion with a clay filler. Even though invention can be used for both asphalt based and coal tar based sealers, the invention will be described with respect to its use in coal tar emulsion type sealers normally applied to asphalt surfaces, such as parking lots and driveways. The invention specifically involves a novel clay powder to form the filler for an asphalt sealer. Thus, clay products and clay filler for a sealer constitute the general technology of the invention.
Many patents have issued relating to and describing the asphalt sealer technology to which the present invention is particularly directed. Representative patents are Walaschek U.S. Pat. No. 3,835,117; Hergenrother U.S. Pat. No. 4,222,916; Ladish U.S. Pat. No. 4,544,690; and, Boyer U.S. Pat. No. 6,361,591. These patents discuss coal tar emulsion type sealers which constitute the end use for the primary aspect of the present invention and is a secondary aspect of the invention. Thus, these patents are incorporated by reference herein as background information. They describe ultimate use for the primary aspect of the invention. Furthermore, a novel coal tar or asphalt sealer is obtained by employing the primary aspect of the invention. These patents explain the general technology of asphalt sealers.
In these prior art sealer patents and in the asphalt sealer technology in general, processed sand is added to the sealer at the sealer mixing plant. Crushed sand, i.e. fracture silica, combines with the other ingredients to obtain the desired thixotropic nature of the applied sealer. Sand added to the sealer, even though ground, has a relatively large particle size since the cost of reducing the grain size of sand is quite high. Furthermore, the emulsion with clay filler must be made viscous enough to maintain in suspension these large sand particles added to the sealer at the sealer mixing plant. This may not be the optical thixotropic characteristic for applying the sealer or for rapid setting of the sealer. As explained in the prior art incorporated by reference herein, the added sand does, indeed increase the wear characteristics of the sealer and also the coefficient of friction to prevent slippery outer surface for the sealer as it sets. For these and other properties, the added sand in the sealer is believed to be essential to create the desired mechanical and rheological characteristics of the sealer as it is applied and ultimately set for long time use.
In summary, the second aspect of the present invention is a novel asphalt sealer of the type utilizing coal tar or asphalt emulsion with a clay filler and silica or sand for creating the desired characteristics set forth in the many patents directed to this type emulsion sealer.
The primary aspect of the invention relates to a novel clay product for shipment to a mixing plant to make the novel sealer. With respect to the novel clay product, there is substantial background technology regarding processing of natural clays into commercial products. The preferred clay used in the present invention is ball clay composed mainly of mineral kaolinite. It is somewhat different than kaolin because of the other minerals in ball clay. Ball clay has a finer grain size and is a very plastic, refractory bond clay. Most ball clays contain a minor amount of organic material and clay mineral montmorillonite. The fineness of the ball clay, together with the added materials give ball clays excellent elasticity and strength. Commercial deposits of ball clays are located in western Kentucky, western Tennessee, northern Mississippi and northeastern Texas. They include Kaolinite, Illite and Smectite with indigenous silica. The use of fine clay in asphalt sealers allows excellent emulsification of the coal tar or asphalt pitch. The fine grain stabilizer of the aqueous emulsion. The present invention relates to a processed ball clay product, specifically developed for use in coal tar emulsions for asphalt sealers. Ball clay is the subject of many prior art patents such as Windle U.S. Pat. No. 4,061,502. This patent teaches a method of using a wet process to purify ball clay. Processing ball clays and, indeed, other clays using complex slurry technology is well known for use in slip casting. A summary of this slurry processing technology is found in Kohut U.S. Pat. No. 5,153,155. In both the Windle patent and the Kohut patent, the starting clay has substantially less than 10% free “SiO2” particles. The Windle and Kohut patents are incorporated by reference to show certain background technologies for wet processing ball clays by a method not material to the processing technique of the present invention. In Kohut U.S. Pat. No. 4,812,427, Kohut U.S. Pat. No. 4,812,428 and Kohut U.S. Pat. No. 4,880,759 there are described a clay slurry process. Such clay slurry type processing is described in Thomas U.S. Pat. No. 7,091,148, which involves a slurry developed specifically for slip casting. A continuation-in-part application of the Thomas patent is disclosed in Pub. No. U.S. 2005/0266978. These two patents items by Thomas are also incorporated by reference herein as illustrating a wet slurry technology, such as described in the two earlier Kohut patents; The wet process involves screening to regulate large or over-sized grain size. The present invention does not relate to a clay material having large particles, nor is it a clay product formed for slip casting. Thus, these patents incorporated by reference herein are mere background information on clay processing. They are relevant as support for the advancement obtained by the present invention which involves a ball clay material developed specifically for an aqueous emulsion type sealer for asphalt surfaces. Its characteristics are tailored to a use not similar to slip casting. In view of this background technology and incorporated prior art patents, it is clear that they do not teach or suggest the invention or inventions defined in the appended claims.